The newest study, published March 14, suggests a potentially powerful link between regular aerobic exercise and a lower risk of dementia.

Shutterstock

A
study published this week in the journal Neurology suggested
that women who were physically fit in middle age were roughly 88%
less likely to develop dementia (defined as a decline in memory
severe enough to interfere with daily life) than their peers who
were only moderately fit.

Neuroscientists from
the University of Gothenburg in Sweden studied 191 women whose
average age was 50 for 44 years. First, they assessed their
cardiovascular health using a cycling test and grouped
them into three
categories: fit, moderately fit, or unfit.

Over the next four decades, the researchers regularly screened
the women for dementia. In that time, 32% of the unfit women were
diagnosed with the condition; a quarter of the moderately fit
women did. But only 5% of the fit women developed dementia.

Despite that strikingly positive finding, the research only
showed a link between fitness and decreased dementia risk; it did
not prove that one caused the other. Still, the work builds on
several other studies that suggest a powerful tie between
exercise and brain health.

Workouts may protect your immune system from some age-related decline as well.

The cyclists were found to have more muscle mass and strength,
and lower levels of body fat and cholesterol than the sedentary
adults. The athletic adults also appeared to have healthier and
younger-looking immune systems, at least when it came to a
key organ
called the thymus.

The study found that the thymus glands of the older cyclists
looked like they belonged to younger people - their bodies were
producing just as many T cells as would be expected from the
thymus of a young person.

"We now have strong evidence that encouraging people to commit to
regular exercise throughout their lives is a viable solution to
the problem that we are living longer but not healthier,"
Janet Lord, the director of the Institute of Inflammation and
Aging at the UK's University of Birmingham, said in
a statement.

Cardio tones your muscles.

Shutterstock

It was initially believed that when it comes to building
muscle, cardio paled in comparison to exercises like resistance
training, which are designed to help you gain strength. But a
recent review of 14 studies published
in the journal Exercise and Sport Sciences Reviews found that
on average, men who did 45 minutes of moderate to intense cardio
4 days a week saw a 5%-6% increase in leg muscle size.

"Aerobic exercise, if done properly, can lead to as much
muscle growth as you'd expect with resistance exercise," Ball
State University exercise scientist Matthew Harber, who authored
the study,
told Men's Fitness.

Cardio exercise may even help reverse some heart damage from normal aging.

Shutterstock

Many of us become less active as we get older. Over time, this
can lead some muscles in the heart to stiffen. One of those
at-risk muscles is in the left chamber of the heart, a section
that plays a key role in supplying the body with
freshly-oxygenated blood.

A recent study split 53 adults into two groups, one of which did
two years of supervised exercise four to five days per week while
the other simply did yoga and balance exercises. At the end of
the
study, published in January in the journal Circulation, the
higher-intensity exercisers saw significant improvements in their
heart's performance. Those results suggest that some stiffening
in the heart can be prevented or even reversed with regular
cardio.

"Based on a series of studies performed by our team over the past
5 years, this 'dose' of exercise has become my prescription for
life," Benjamin Levine, the author of the study and a professor
of internal medicine at the University of Texas Southwestern,
said in a statement.

Aerobic exercise "has a unique capacity to exhilarate and relax,
to provide stimulation and calm, to counter depression and
dissipate stress," according to an article
in the Harvard Medical School blog "Mind and Mood."

The reason aerobic workouts lift our spirits seems related to
their ability to reduce
levels of natural stress hormones, such as adrenaline and
cortisol, according to a recent study in the Journal of Physical
Therapy Science. Activities like running and swimming also
increase
overall blood flow and provide our minds fresh
energy and oxygen - another factor that could help us feel
better.

Heart-pumping workouts appear to have a positive impact on your gut.

Those microbes play a role in inflammation levels, which can be
an early warning sign of illness.

The researchers had study participants exercise three to five
times per week for six weeks, and observed increases in
their concentrations of butyrate, a type of fatty acid that helps
keep our guts happy by tamping down on inflammation and producing
energy.

"These are the first studies to show that exercise can have an
effect on your gut independent of diet or other factors,"
Jeffrey
Woods, a professor of kinesiology and community health at the
University of Illinois who led the research,
said
in a statement.

Cardio may improve cholesterol levels, too.

sportpoint/Shutterstock

A large
recent review of research on how cardio affects cholesterol
levels looked at 13 studies on the topic. It found that aerobic
exercise was tied with reductions in LDL, which is also known as
"bad" cholesterol because it can build up on the walls of
your arteries and raise your risk of heart
disease.

Cardio exercise was also linked with increases in HDL, also known
as "good" cholesterol because it mobilizes the cholesterol
in your blood.

"Prolonged moderate-intensity aerobic exercise should be
recommended as a starting point for those who have previously
been sedentary or are new to exercise," the authors wrote.

Aerobic exercise helps prevent and manage diabetes by improving the way the body uses blood sugar.

Getty Images / Anthony Kwan

Several studies have found that cardio exercise helps people both
prevent Type 2 diabetes and manage its symptoms - mostly by
improving the way the body uses blood sugar.

It's not yet clear why our workouts appear to play a role
in skin health, but the researchers found elevated levels of a
substance critical to cell health called IL-15 in skin samples of
participants after exercise. That finding that could shed light
on why cardio seems to make our skin look better.

Workouts may reduce the symptoms of depression.

In addition to boosting the moods of healthy people,
aerobic exercise may have a uniquely powerful positive impact on
people with depression.

In a pilot
study, people with severe depression spent 30 minutes
walking on treadmill for 10 consecutive days. The researchers
found the activity was "sufficient to produce a clinically
relevant and statistically
significant reduction in depression."

Cardio appears to guard against some age-related decline like reduced brain connectivity.

Shutterstock

As we age, the brain - like any other organ - begins to
work less efficiently, so normal signs of decline begin to
surface. Our memory might not be quite as sharp as it once was,
for example.

A study published in May looked at adults with MCI between
the ages of 60-88, and had participants walk for 30
minutes four days a week for 12 weeks. The results showed
strengthened connectivity in a region of the brain where
weakened connections have been linked with memory loss. That
development, the
researchers noted, "may possibly increase cognitive reserve,"
but more studies are needed.

Aerobic exercise may help protect against memory difficulties in people undergoing chemo as well.

cdrin/shutterstock

In a July study, researchers examined hundreds
of breast cancer survivors to see if activities like
walking and swimming have an effect on "chemo brain," a commonly
reported side effect of breast cancer treatment that involves
memory loss and difficulties focusing.

They gave nearly 300 breast cancer survivors accelerometers to
track their activity, and provided them with an iPad app that featured
quizzes designed to measure their attention and memory. At the
end of a week, people who'd done aerobic exercise every day were
significantly less tired than those who did little to no
exercise, and also performed better on the app's quizzes.

"The message for cancer patients and survivors is, get
active!" Diane Ehlers, the lead author on the study
and a professor of exercise psychology at the University of
Illinois at Urbana Champaign,
said in a statement.

Cardio may also be tied to increases in the size of brain areas linked to memory, but more research is needed.

For the study, 86 women with MCI between 70 and 80 years
old were randomly assigned to do one of three types of exercise
twice a week for six months. Some did aerobic training (like
walking and swimming), others focused on resistance training
(like weight-lifting), or balance training.

Afterwards, only the women in the aerobic group were found
to have significant increases in hippocampal volume, but more
studies are needed to determine what effect this has on cognitive
performance.